TRUCK SERVICE MANUAL
ENGINE
The PT fuel system consists of the fuel pump, supply
PT (type G) Fuel Pump
lines, drain lines, fuel passages and injectors. Fig. 5-1
The PT (type G) fuel pump assembly, Fig. 5-3, is made
There are four types of PT fuel pumps. The first type
up of three main units, the gear pump, standard governor
called PT (type G) is shown in Fig. 5-3.
and, throttle.
Gear Pump And Pulsation Damper
The gear pump is driven by the pump main shaft and
contains a single set of gears to pick up and deliver fuel
throughout the fuel system. Inlet is at the rear of the
gear pump. A pulsation damper mounted to the gear
pump contains a steel diaphragm which absorbs
pulsations and smoothes fuel flow through the fuel
system. Automotive engines also may have fuel filter
mounted to damper. From gear pump, fuel flows
through the filter screen and to the. governor assemblies
as shown in Fig's. 5-3,
Throttle
The-throttle provides a means for the operator to
manually control engine speed above idle as required by
varying operating conditions of speed and load.
Fig 5-1, (FWC-13) Fuel flow diagram - PT (type G)
In the fuel pump, fuel flows through the governor to the
pump- inline engine
throttle shaft. At idle speed, fuel flows through the idle
port in the governor barrel, past the throttle shaft. To
Fuel Pump
operate above idle speed, fuel flows through the main
The fuel pump is coupled to the compressor, vacuum
governor barrel port to the throttling hole in the shaft.
pump or fuel pump drive which is driven from the engine
gear train. Fuel pump main shaft in turn drives the gear
Governors
pump, governor and tachometer shaft assemblies.
The "standard" governor is actuated by a system of
springs and weights, and has two functions:
1. The governor maintains sufficient fuel for idling with
the throttle control in idle position.
1 TACHOMETER SHAFT
2 FILTER SCREEN
3 FUEL TO INJECTORS
4 SHUT-DOWN VALVE
5 GEAR PUMP
6 CHECK VALVE ELBOW
7 FUEL FROM TANK
8 PULSATION DAMPER
9 THROTTLE SHAFT
10 IDLE ADJUSTING SCREW
11 HIGH SPEED SPRING
12 IDLE SPRING
13 GEAR PUMP PRESSURE
14 FUEL MANIFOLD PRESSURE
15 IDLE PRESSURE
16 GOVERNOR PLUNGER
17 GOVERNOR WEIGHTS
18 TOROUE SPRING
19 GOVERNOR ASSIST PLUNGER
20 GOVERNOR ASSIST SPRING
21 MAIN SHAFT
Fig. 5-3. (FWC-31) PT (type G) fuel pump and fuel flow
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